<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="utf-8">
	<title>Docment</title>
	
	<style>
		div.red{
			color:red;
		}
		.a.b.c{
			font-size:40px;
		}

		h1,span{
			color:blue;
		}

	</style>

</head>
<body>
	<div class="red"> im div</div>

	<p class="red">p元素</p>

	<div class="red2 a b c">div 标签</div>

	<p>又是p元素</p>

	<h1 class="h">标题</h1>

	<span>选中文字</span>
</body>
</html>